In situ and Real-Time Surface-Enhanced Infrared Study of Electrochemical Reactions

Abstract

Surface-enhanced infrared absorption spectroscopy (SEIRAS) in conjunction with cyclic voltammetry has been applied to in situ and real-time monitoring of the electrochemical redox reactions of heptylviologen at a silver electrode surface. The high sensitivity of SEIRAS enables the real-time spectral monitoring of the irreversible reaction processes on the millisecond time scale with rapid-scan interferometry. With the combination of the molecular information obtained from the spectra and the kinetic data obtained by cyclic voltammetry, the complex voltammetric behavior of the molecule can be discussed in detail at the molecular scale. The results demonstrate the utility of the real-time infrared monitoring in analyzing electrochemical reactions.

Two-dimensional assembly and local redox-activity of molecular hybrid structures in an electrochemical environment

“…The observed spectroscopic bands below 1750 cm À1 represent vibration modes of the bipyridinium ring having dipole moment components either parallel to the longer molecular axis, as defined by the 4,4 0 -N,N 0 -direction (B 2u in D 2h symmetry; 1641, 1508, 1222 and 1181 cm À1 with the latter dominated by the N-(CH 2 ) n -R stretching vibration), or perpendicular to this axis (B 3u modes in D 2h symmetry; 1560, 1448, 1345 cm À1 ). [78][79][80][81][82][83] The positions of the methylene C-H-stretching modes provide a measure of the intermolecular environment of the alkyl chains in the molecular assembly. The peak frequencies of u s (CH 2 ) (2865 vs. 2850 cm À1 ) and u a (CH 2 ) (2939 vs. 2920 cm À1 ) in the liquid state are typically higher than those for a highly ordered crystalline polymethylene chain.…”

“…[78][79][80][81][82][83] The IR spectrum of the electrochemically generated dimer species is interpreted by the vibronic coupling in a one-dimensional charge transfer complex. 82 The negative band around 1100 cm À1 indicates the release of perchlorate ions upon the reduction V 21 2 V 1d . The radical cation monomer is stabilized in a hydrophobic environment 80 and by electrostatic attraction to co-adsorbed ClO 4 À anions.…”

“…3E) demonstrate that the stability of the radical cation monomer appears to be higher in the monothiol adlayer. The formation of the radical cation dimer for the dithiol adlayer is facilitated by stronger p-interactions between the radicals compared to Coulomb interactions between radical monomers and anions, 82 as well as by the matching in the commensurability of the intra-assembly planes. 86 A comprehensive analysis of the steady state and time-resolved ATR-SEIRAS experiments on the self-assembly and electroreduction of HS-6V6-H and HS-6V6-SH on gold Au(111, 25 nm) will be given elsewhere.…”

Surface-Enhanced Infrared Absorption

“…The enhancement is significant for the first monolayer directly attached to the surface and decays sharply within about 5 nm from the surface [10,22,23,24,25]. 5.…”

ATR-SEIRAS study of CO adsorption and oxidation on Rh modified Au(111-25 nm) film electrodes in 0.1 M H2SO4

“…This effect allows distinguishing the orientation of adsorbed molecules. Direct access to chemical information on structure and dynamics of the electrode/electrolyte interfaces can be provided by this in situ spectroscopic approach, which has been employed as a powerful tool in the investigations of catalytically-active solid/liquid interfaces [38][39][40][41]. However, the ATR-SEIRAS technique requires the use of thin film electrodes, which usually have a less ordered surface structure than bulk single crystal electrodes.…”